WASHINGTON, D.C. - Employing a worldwide battery of small telescopes over several years, astronomers have done something the Hubble Space Telescope can't do: peering deep into the disk of material around a newborn Sun-like star they detected what might be a developing planet.
Further study of the system is expected to provide important insight into how and when planets are born around stars like our Sun.
Since the late 1990s, the astronomers have known that the star, called KH 15D, winks. In recent months they figured out that one or possibly two blobs of material -- probably dust and possibly some asteroids, too -- orbit very close to the star and eclipse it.
"Essentially the star winks at us," said William Herbst of Wesleyan University.
The blobs, assuming there are two, could have been created by a larger object, the possible planet that would have evolved during the star's young life. The object might be a small star, however. Further observations will be needed to learn exactly what it is.
The discovery was presented at a press conference here today at Carnegie Institution during a four-day meeting titled "Scientific Frontiers in Research on Extrasolar Planets."
Other researchers have imaged and studied so-called protoplanetary disks around other stars. These dust disks are remnants of star formation and thought to be the birthplaces of planets. Dust coalesces into rocks, the theory goes, and rocks collide and make planets.
No one knows how long the process takes, however.
KH 15D is about 2,400 light-years from Earth. It is very similar to our Sun yet very young -- just 3 million years old. The Sun is about 4.6 billion years old. The intriguing possibility of a planet around such a young star would help astronomers improve their models of planet formation, said Alan Boss, a planet formation expert at the Carnegie Institution who was not involved in the new work.
The newly studied system could eventually shed light on the earliest stages of planet formation, Boss said.
The eclipsing material is closer to the star than Mercury is to our Sun. Astronomers have never directly measured material this close to a star. One expert said even the Hubble Space Telescope could not see things this close to a star.
"This gives us a chance to see what's happening right down in the maelstrom where terrestrial planets [like Earth] form," Boss said.
The data on the inner object, be it a planet or a star, is not firm. Herbst and his colleague, Catrina Hamilton, stressed that more observations are needed to confirm how the system is structured. If an object is determined to be there, its effect on the dust disk would be something like the Moon's pull on Earth's oceans, which creates a high tides on opposite sides of the planet.
These tides, called gravity density waves when referring to dust disks, would explain the eclipse. Every 48 days, the star's light drops to about 4 percent of its maximum. Astronomers have observed eclipses of other stars, but these are typically caused by large companion stars or other objects.
In this case, the slow onset of the eclipse implies its cause is something shaped more like a wave -- a long string of material. Further, the eclipses are not the same, implying they are caused by two waves of material with slightly different properties, the researchers said.
"It might be two blobs, it might be one," Herbst said. "We're really not sure."
He added that sorting out what's going on will "probably take years and years."
Importantly, the researchers have detected changes to the blobs in recent months. No one has observed other possible protoplanetary disks long enough to spot changes over time.
Herbst and Hamilton employed researchers and telescopes around the world to collect data for full 24-hour periods -- not possible from a single location. Researchers in Uzbekistan, Israel, Germany and several American institutions contributed observations.
advertisement
